Speed control of BLDC motor for five-level DC-DC converter with asymmetrical control strategy

Abstract

In this project, an asymmetrical duty cycle control strategy was proposed to the TPTL dc/dc converter. The modified converter remains all the advantages of original control strategy; meanwhile, soft-switching can be achieved using the energy stored in output filter inductance and leakage inductances of transformers (or resonant inductances).Three-phase three-level (TPTL) dc/dc converter has the advantages of lower voltage and current stress on switches, which is suitable for high power and high input voltage applications. Adopting a symmetrical control strategy, the ripple frequency of input and output current can be increased significantly, resulting in a reduced filter requirement. However, all the switches are hard-switching, leading to a considerable switching loss. Full-bridge dc/dc converters have been used widely in the medium-to-high-power applications for the pulse width = modulation (PWM) control, soft-switching characteristics, and lower power rating on switches. To further reduce the current stress on switches for higher power level requirements, a prominent three-phase full-bridge topologies was first put forward by Ziogas for medium-voltage-level applications [1], in which three-phase bridges consisting of six switches and a three-phase transformer are adopted. With the three-phase architecture, the converters has the superior features, including lower current rating of switches, reduced input and output current ripple allowing small size filter requirement and better utilization of transformer core. The improved resonant converter features zero-voltage-switching (ZVS) realization under wide load range and higher conversion efficiency. However, wide variation in switching frequency should be concerned in the applications with wide input/output voltage range. Other alternative solutions are the non resonant soft-switching three-phase converters. in order to obtain ZVS commutation for all switches and control the output voltage, Nevertheless, the upper and lower commutation cell switches are subjected to different current stresses) is improved by using MAT Lab/Simulink. The proposed concept can be implemented with five levels the proposed concept can be implemented for speed control of BLDC motor using Matlab/Simulink software